Vacuum tube termination



March 18, 1969 w J HUDSON, ET AL 3,434,097

VACUUM TUBE TERMINATION Filed Oct. 5, 1967 INVENTORS WILLIAM JEFFREY HUDSON JOHN WILLIAM GAW E257. 4Q BY M March 18. 1969 w. J. HUDSON, JR, ET 3,434,097

VACUUM TUBE TERMINAT I ON M I K m /5; SYN 2 V. wa TFM t it e EJL/ m m 5 m L H ww United States Patent 3,434,097 VACUUM TUBE TERMINATION William Jeifrey Hudson, Jr., Harrisburg, and John William Gaw, Elizabethtown, Pa., assignors to AMP Incorporated, Harrisburg, Pa.

Filed Oct. 3, 1967, Ser. No. 672,566 U.S. Cl. 33989 Int. Cl. HOlr 13/54, 33/74; H01j 9/18 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Termination of vacuum tube like devices requiring a high voltage supply has long been a problem. In part, the problem is due to the fact that the tube envelope is typically of a hard, fragile material such as glass, through which must be passed a conductive member which in turn must be terminated to high voltage leads. To avoid breakage of the conductive member or of the envelope, the prior art approach has been generally one of permanently aflixing high voltage supply leads to the tube at the site of passage of the conductive member with a length of lead being provided to go directly to the tube power supply, or, if a disconnect/ connect function is desired to a connector at an end of the lead well removed from the tube itself. This practice results in a cumbersome tube assembly with one or more relatively long leads strung oh the end of the tube to create problems in shipment, in handling and in installation of the tube and lead assembly into the equipment of use. Moreover, if the tube is of a type which must be frequently replaced, each replacement must be accompanied by a restringing of the tube leads through and within the chassis of the equipment served by the tube. General dissatisfaction by both tube manufacturers and users has been expressed with this answer to the problem, and numerous attempts have been made to provide a connector which fastens directly onto the tube. Connectors of this type may be found in the prior art and all seem to have one shortcoming or the other. The prior art connectors which provide an adequate mechanical connection of an associated lead or leads permit, if not encourage, pin and envelope breakage. Connectors in accordance with the prior art which snap on or slide on do not adequately eliminate air spaces and accompanying corona discharge which can cause poor circuit performance and eventually voltage breakdown and a resulting destruction of the high voltage supply lead assembly.

SUMMARY OF THE INVENTION The present invention relates to a method and means for terminating vacuum tubes and like devices having a high voltage supply.

It is an object of the invention to provide a high voltage termination of vacuum tubes and like devices which permits a high voltage lead to be connected and disconnected at the surface of a tube through a connector construction which is simple in terms of application and inexpensive in terms of parts required. It is another object to provide a high voltage connect/ disconnect termination for vacuum 3,434,097, Patented Mar. 18, 1969 'ice tubes and the like which is mechanically adequate, but which minimizes the risk of fracture of a tube envelope or damage to the conductive member used therein. It is still another object of the invention to provide a high voltage connect/ disconnect technique which is corona resistant and at the same time facilitates a tube replacement relative to a power supply.

The technique of the invention contemplates the use of a bead or cup of glass material containing a conductive pin extended therethrough and fused therein which bead or cup is, in turn, fused in the wall of a glass envelope of a vacuum tube. An insulating bushing of glass or insulating plastic, such as epoxy material, is fitted over the pin and into a surrounding head of adhesive material, such as a standard silicone adhesive. The bushing is of a type permitting the insertion of a conductive lead therewithin and over the pin, such lead containing a contact receptacle member and being dimensioned substantially to fill the bushing to eliminate air voids. A member adapted to mate with the bushing to force the lead axially within the bushing and maintain the lead against pull-out is provided which requires a twisting motion for insertion or for withdrawal. The bond of the bushing to the tube serves to preclude fracture of the tube envelope by twisting. The bond also precludes pin breakage or breakage of the seal between the pin and the glass material of the bead or cup by axial loads inadvertently placed upon the lead. The assembly is readily repairable and may be installed or repaired in the field, with only a reapplication of standard adhesive.

In the drawings:

FIGURE 1 is a sectional view of a portion of a vacuum tube envelope having a hole therein through which is to be passed a high voltage terminal;

FIGURE 2 is a view of the structure of FIGURE 1 with a glass bead carrying a terminal mounted within the aperture therein and fused thereto in a position of use;

FIGURE 3 is a longitudinal and sectional view of an assembly in accordance with the invention prior to installation on the structure shown in FIGURE 2;

FIGURE 4a is a sectional view of the structure of FIGURE 2 with a bead of adhesive applied thereto;

FIGURE 4b is a longitudinal and sectional view of the component shown in FIGURE 3 following installation in accordance with the invention;

FIGURE 5 is a longitudinal and sectional view of components of the assembly of the invention prior to in- Stallation on a tube of a different construction; and

FIGURE 6 is a view of the components of FIGURE 5 following installation in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGURE 1 the element 10 represents the portion of the glass envelope of a vacuum tube. Numeral 12 represents an aperture in such envelope through which is to be passed a conductive member intended to carry the high voltage requirements of the tube. FIGURE 2 shows the aperture 12 filled with a head 14 fused as at F, to the material of 10. The bead 14 is also fused as at F to a conductive member 16, the end within the tube extending to the tube electrode structure and the end outside the envelope extending for a length as shown, The member 16 is of a suitable material to permit fusion to the glass material of the bead, such materials typically being Kovar or a relatively low resistance steel alloy.

In FIGURE 3 a bushing 18 is shown aligned for positioning on the member 16. The bushing 18 is typically of an insulating plastic material, such as glass-filled epoxy having insulating and dielectric properties and being sub- 3 stantially rigid. The outside upper end of 18 is threaded as at 20 in the manner indicated in FIGURE 3 and there is included within the main portion of 18 a bore shown as 22. Toward the bottom of 22 is an inwardly directed flange 24, carrying in the center thereof a small aperture 26 which is of a diameter to just fit over the member 16. Beneath 24 is a recess 28, having a purpose to be described. Axially aligned in FIGURE 3, but prior to insertion with the bore 22, is a high voltage lead 30 comprised of a core of stranded conductor members 32, surrounded by a relatively thick and flexible dielectric sheath 34 of a material capable of withstanding substantial stress without breakdown. The lead 30 in use extends to a high voltage power supply. Within the inside of the end of the lead is a contact member 36 terminated as by crimping or soldering to the core 32 and having in the forward end a spring portion 38 adapted to define a receptacle receiving the end of member 16. The sheath 34 is extended over 36 in a snug fit to minimize air voids. Fitted on the lead 30 is a nut 40 internally threaded as at 42 with a threading adapted to mate with the threading 20, on bushing 18. The back end of the nut contains a bore 44 through which is fitted the lead 30. An O-ring 46 is fitted within the nut and surrounding the lead. The O-ring is of a resilient and flexible material adapted to be deformed upon threading of the nut onto the bushing so as to seal the lead at the point of entry into the bushing and to hold the lead against axial pull-out up to a reasonable pull-out force.

Reference is made to US. Patent No. 3,163,692 granted Dec. 29, 1964, to W. A. Smith et al. for a disclosure of a preferred method for making a lead having a structure like that shown in FIGURE 3. Reference is also made to US. Patent No. 2,958,844 granted Nov. 1, 1960, to W. A. Smith et al., for a disclosure of a connector having the general configuration of the components shown in FIGURE 3, but with the conductive member like 16 affixed within the bushing by a metallic disc.

In accordance with the present invention, a tube having a conductive member like 16 secured in the manner shown in FIGURE 2, is fitted with a high voltage assembly in the following manner. A bead of adhesive material shown as 50 is laid around the conductive member 16 in the manner shown in FIGURE 4a. The amount of material 50 and the disposition should be controlled so as to fill the bore 28 as bushings 18 are fitted over member 16 and pushed in against the bead 14 with a web of material being forced to engage and surround the outside of the end of the bushing. FIGURE 4b depicts the adhesive material as distributed and as it appears following curing. The bushing 18 mounted as in FIGURE 4b, is effectively mechanically connected to the tube envelope by the bond between the adhesive and the glass of the envelope and the material of the bushing. A high voltage lead like that described may then be inserted within the bushing and secured to the tube in the manner depicted in FIGURE 4b. A suitable adhesive which bonds to glass and to epoxy and which has been found to work well in the application just defined is Dow Corning Co. No. 140 Silicone Adhesive. This kind of adhesive is flexible and resilient when cured in its stable state. Other adhesives are, of course, contemplated which if not flexible will at least shear to prevent overload and breakage of the tube envelope or pin.

As will be discerned from FIGURE 4b, a substantially void-free termination of a high-voltage lead is provided to a glass envelope. Any slight bending movement in an axial sense of the lead or the bushing will be accommodated by the flexible bond of adhesive. Inadvertent overtightening of the nut of the assembly will not fracture either the envelope or the bond between the conductive member 16 and the glass bead through which it is fitted, the adhesive first tending to give and then breaking free if the torsional load is too great. In this event, the union between the components may be quickly and easily restored by a fresh appliaction of adhesive. Even excessive axial pull-out of the lead should not serve to fracture the envelope because with the invention assembly the whole bushing can be pulled off of the envelope leaving the conductive member 16 in position. The invention technique and assembly thus far shown provides a corona resistant and mechanically adequate connection of a high voltage lead to a vacuum tube, which is more than adequate within a wide range of mechanical loading of the part for normal use. On the other hand, it precludes fracture of the tube and it permits a connect/disconnect function directly at the place of the tube, which is highly desirable from the standpoint of tube manufacturers and of those who use tubes, and must install leads from power supplies to such tubes and must, at times, replace the tubes.

Referring now to FIGURE 5, an alternative embodiment is shown with an identity of connector and conductive parts, but with a different type of envelope. The envelope shown as 52 has a cup shaped insert fused as at F to a portion of the tube. This cup shaped insert includes the cylindrical wall shown as 54, which extends up in surrounding relationship relative to the conductive member 16. FIGURE 6 shows the connector assembly of the invention mounted within the cup shaped insert with adhesive material 56 made to extend around the bushing 18 and within the walls 52 of the insert. As in the previous example, the connector components are mechanically secured to the envelope in a manner which will facilitate torsional loading thereof without fracture of the envelope and which will tolerate some bending movement of the bushing without fracture. The assembly does facilitate a connect/ disconnect function of a high voltage lead directly at the face of a vacuum tube.

It is to be noted that the only metal employed with the assembly, other than the conductive lead and socket, is that of the conductive pin which is part of the tube, not of the connector. Minimization of metallic parts in areas of high stress is particularly advantageous.

Having now described the invention in terms intended to enable the preferred mode of practice thereof, the invention is defined through the appended claims.

What is claimed is:

1. In a method of terminating a high voltage lead to a structure having a glass envelope, the steps comprising providing an elongated separable conductive terminal member fused to a glass bead so as to be rigidly secured thereto and extend therethrough, fusing said glass head with the material of said envelope to effect the seal of said envelope relative to said conductive terminal member with said terminal member extending outwardly from said envelope, providing a high voltage lead connector assembly including an insulating bushing having an aperture therein to receive the conductive terminal member fitted therethrough in an annular recess in the end of said bushing through which said conductive terminal member is extended, placing a bead of adhesive, insulating material about the said conductive terminal member adjacent said glass bead and forcing said bushing into said material and against said glass bead to provide a bond therebetween, the said conductive terminal member then being extended within said bushing for termination to a conductive means fitted therewithin and held therein by a portion of said connector assembly mated with said bushing.

2. The method of claim 1 wherein the said adhesive, insulating material is limited in quantity and is made to have characteristics of adhesion whereby to be separated from said glass material if undue forces are applied to said connector assembly, to prevent fracture of said envelope.

3. The method of claim 1 wherein the said adhesive, insulating material is made to be flexible in its cured stable state whereby to accommodate slight relative movement between said connector assembly and said envelope.

4. In a connection of a high voltage lead assembly to a vacuum tube or the like, a high voltage connector including a bushing having a first bore therein to receive the insulating sheath of a conductive lead substantially filling the volume thereof and means to hold said conductive lead within said bore, a second smaller bore therein at an opposite end to receive a charge of adheseive material, a contact receptacle terminated to the conductive core of said lead and positioned within said sheath within said bore, a glass envelope for a vacuum tube or like device including a glass insert fused to the material thereof carrying a conductive pin extending within said envelope and outwardly therefrom, said conductive pin being of a dimension to fit within the said receptacle through said second bore, the connector portion including the second bore being mechanically affixed to the said envelope through an adhesive material having characteristics in its cured stable state permitting a breakage of the bond of said connector rather than of said envelope.

5. A high voltage connector for use with vacuum tubes and the like having a glass envelope and a conductive pin extending therefrom including a connector having a bushing into which is fitted a high voltage lead, means for mechanically holding said high voltage lead within said bushing, the said lead having a receptacle fitted therewithin and within said bushing to engage said pin, a flange within the lower portion of said bushing including an aperture adapted to receive in a tight fit the said pin inserted therein, the said bushing having an annular recess adjacent said aperture to define a reservoir for adhesive material, said flange operating to preclude flow of material into other portions of said bushing.

6. The connector of claim 5 wherein said conductive pin, which is part of said tube or the like, extends through said reservoir into said bushing and into said receptacle.

References Cited UNITED STATES PATENTS 1,727,826 9/ 1929 Harris 339- X 2,292,002 8/ 1942 Yamashita 339-145 2,486,497 11/ 1949 Salneu 2925.15 2,535,773 12/1950 Yoder 339-145 X 2,813,922 11/1957 Arnold l7450.52 3,242,253 3/ 1966 Bailey et al l74--50.58 3,278,886 10/1966 Blumenberg et al. 339145 FOREIGN PATENTS 190,162 6/ 1957 Austria.

RICHARD E. MOORE, Primary Examiner.

US. Cl. X.R. 2925.15; 339-144 

